11

5016HS–SMEM–11/08

AT88SC12816C

Figure 12. Write Lock Example

The write lock byte may also be locked by writing its least significant (rightmost) bit to “0”. More-

over, when write lock mode is activated, the write lock byte can only be programmed – that is,

bits written to “0” cannot return to “1”.

In the write lock configuration, only one byte can be written at a time. Even if several bytes are

received, only the first byte will be taken into account by the device.

Password

Verification

Passwords may be used to protect read and/or write access of any user zone. When a valid

password is presented, it is memorized and active until power is turned off, unless a new pass-

word is presented or RST becomes active. There are eight password sets that may be used to

protect any user zone. Only one password is active at a time, but write passwords give read

access also.

Authentication

Protocol

The access to a user zone may be protected by an authentication protocol. Any one of four keys

may be selected to use with a user zone.

The authentication success is memorized and active as long as the chip is powered, unless a

new authentication is initialized or RST becomes active. If the new authentication request is not

validated, the card loses its previous authentication and it should be presented again. Only the

last request is memorized.

Note:

Password and authentication may be presented at any time and in any order. If the trials limit has

been reached (after four consecutive incorrect attempts), the password verification or authentica-

tion process will not be taken into account.

Figure 13. Password and Authentication Operations

Address

$0$1$2

$3

$4$5$6

$7

$080

11011001

xxxx xxxx

xxxx xxxx

xxxx xxxx

xxxx xxxx

xxxx xxxx

xxxx xxxx

xxxx xxxx

locked

locked

locked

CS

VERIFY CS

Write DATA

VERIFY RPW

DATA

Checksum (CS)

VERIFY CS